Multifunctional 1,4-Diazabicyclo[2.2.2]octane Cross-Linked Poly(2,6-dimethyl-1,4-phenylene oxide)-Based Stable AEM for Enhanced Acid Recovery from Metallurgical Wastewater

The safe disposal of industrial wastewater is a major concern for the environment. Membrane-based separation processes can be an alternative to traditional wastewater treatment. Here, an integrated system has been designed and optimized for the effective reclamation of acid from metallurgical wastewater. Herein, we report cross-linking of brominated poly(2,6-dimethyl-1,4-phenylene oxide) using multifunctional 1,4-diazabicyclo[2.2.2]octane (DABCO) for architecting a stable anion exchange membrane (AEM). Varied concentrations of DABCO significantly influenced IEC and ionic conductivity (κ^m) of prepared AEMs. Optimized PPO–DB-60 AEM demonstrated excellent IEC (1.83 mequiv g^–1) and κ^m (4.13 × 10^–2 S cm^–1). Recovery efficiency for HCl, HNO₃, and H₂SO₄ was observed to be 41.5, 29, and 18% with proton diffusion coefficient (μ_H⁺), 4.82 × 10^–3, 2.86 × 10^–3, and 1.57 × 10^–3 m h^–1, respectively. In an integrated system, improved recovery efficiencies with increments of 19.0% (HCl), 12.0% (HNO₃), and 9.0% (H₂SO₄), compared to the standalone diffusion dialysis. Proton diffusion coefficients under these conditions also improved to 6.5 × 10^–3 m h^–1 for HCl, 3.53 × 10^–3 m h^–1 for HNO₃, and 1.88 × 10^–3 m h^–1 for H₂SO₄ sequentially. Moreover, energy consumption (EC) values for the integrated process were 0.716 to 1.026 kWh kg^–1 for different acids with up to 95.38% current efficiencies. These findings underscore the effectiveness of the prepared AEMs for acid reclamation and concentration with an integrated approach for laboratory scale performance.